An example PLL architecture includes a VCO with a frequency control loop that generates a VCO_clock phase-locked to (phase-aligned with) an input reference clock REF-CLK at a loop-controlled frequency. A frequency synthesizer can include the PLL with an input reference divider (RDIV) which divides down REF_CLK for input to the PLL, and/or an output channel divider (CDIV) which divides down the PLL output VCO_clk to provide a channel-divided output PLL_CLK. The VCO loop includes a PD or PFD (phase or phase frequency detector) and a loop filter (such as a charge pump) that provide a VCO frequency tuning voltage/signal to the VCO to control VCO_clk frequency, and a feedback divider (NDIV) that divides VCO_clk to provide an NDIV_out signal to the PFD.
The PFD receives a PFD_clk based on REF_CLK, such as from RDIV, for phase comparison with the NDIV_out feedback from the VCO. Under lock conditions, the VCO loop ensures that the phases of the PFD inputs PFD_clk and NDIV_out (divided VCO_clk) are phase aligned, or the PFD generates a PFD error signal that is accumulated by the loop filter to provide the VCO tuning signal. NDIV effectively provides frequency multiplication, from the REF_CLK frequency to a selected VCO_clk frequency, which is divided back to the REF_CLK frequency (NDIV_out) for phase comparison by the PFD.
NDIV can be an integer N or fractional N.F divider, with the fractional value provided, for example, by a sigma-delta modulator providing fractional input to an integer NDIV (for fractional frequency multiplication). The post-VCO CDIV selectively divides VCO_clk to output the channel-divided PLL_OUT clock. NDIV and/or CDIV can be programmable.
Some applications require multiple clocks, each generated by a separate PLL, with the PLL clocks phase aligned across the multiple PLLs. Example applications are beam forming, phased array radar, and medical scanners. Also, 5G wireless MIMO (Multiple Input Multiple Output) applications require the Multiple Output clocks to be synchronized.
While this Background information references touch input for mobile/personal communication/computing devices, this Patent Disclosure is more generally directed to input button/keys based on touch technology.